The Rolling Chain of Events Behind Texas Blackouts

What happened yesterday to cause the rolling power blackouts across Texas? A chain reaction of problems involving the state's coal and gas appeared to be the cause — and wind plants were having trouble, too.

by Kate Galbraith Feb. 3, 20111 PM

What happened yesterday to cause the rolling power blackouts across Texas?

State Sen. Troy Fraser, R-Horseshoe Bay, in a phone call with the Tribune today, stressed that conclusions are still tentative but said a chain reaction of problems involving the state's coal and gas plants appeared to be the cause — and wind plants were having trouble, too. So far no blackouts have been ordered today.

Electricity demand spiked in Texas yesterday as the cold weather struck, setting a wintertime record for usage. Summer usage is higher, but winter also can bring strong demand because about two-thirds of Texas homes are heated with electricity.

Initially, it appears, some coal plants went offline due to cold-weather problems, taking a large chunk of electricity out of the grid. Luminant, a major power-generation company, confirmed that its two coal units at the Oak Grove plant in Robertson County failed, as did two units at a coal plant in Milam County. "We are in various stages of start-up and operation for that group," Allan Koenig, a Luminant spokesman, said via e-mail. Three of these four units only began operating in the last few years; Fraser, who chairs the Senate Committee on Natural Resources, noted that they had new emissions-control technologies, and said one question was how those technologies had handled the cold.

Dave Knox, a spokesman for NRG, another power company, said that a cold-weather problem also caused a shut-down of its Limestone coal plant near Jewitt, Texas. The problem occurred yesterday, albeit after the early-morning crisis, and the plant returned to operating early this morning. 

Natural gas plants were hastily turned on to make up for the coal-plant failures. But, Fraser said, some power cuts affected some stations for compressing natural gas — so without power they couldn't pump gas, causing some gas power plants to go offline. In addition, rules regarding "curtailment" of natural gas — who gets first dibs on gas when gas supplies are tight — were last revised in 1972, Fraser said, leaving some power plants at risk of losing out on supplies. A large minority of Texans heat their homes with gas, in addition to the needs of the power plants, so there was extremely high demand for gas during the freezing weather.

"We didn't have enough available gas," Fraser said. An affidavit filed yesterday with the Railroad Commission by Trip Doggett, the head of the Eletric Reliability Council of Texas, the state's grid operator, said that "certain gas suppliers may be curtailing natural gas to electric utilities or electric generation customers." Koenig, of Luminant, confirmed that "one of our gas plants has been curtailed due natural gas supply restrictions."

Wind generators also appeared to be having problems, said Fraser; he had received reports of some turbines shutting down because of issues with ice on the blades. "The wind was blowing yesterday, but I'm not sure wind generation was available because they had problems with ice," he said. (At an Iberdrola wind farm near Corpus Christi that the Trib visited yesterday, most turbines were spinning steadily, in response to the grid operator's call for maximum production. But the plant's operator, Daniel Pitts, said that a few machines were having issues because the cold air had affected the nitrogen in the hydraulic system that helps run the turbines.) Dottie Roark, a spokeswoman for ERCOT, said that yesterday morning between 5 a.m. and 8 a.m., about 3,500 to 4,000 megawatts of wind was available (the state has about 10,000 megawatts of wind installed).

Is the problem solved? "We think we're probably going to be okay today, and obviously it's going to warm up from there," said Fraser.

In the next couple of weeks, after the crisis passes, Fraser said he would call a hearing on the blackouts to figure out what happened and how to fix it. He noted that there were "a lot of unusual circumstances" to this storm, and that while Texas was well-prepared for spiking electricity usage in the summer, "to my knowledge we've never been tested for an event during the winter." But it's clearly imperative to fix the system, he said. The Public Utility Commission, which oversees ERCOT, met this morning and is also investigating the cause of the power-plant problems, spokesman Terry Hadley said.

ERCOT said this morning that 3,000 megawatts — the equivalent of nearly twice the output of the Oak Grove coal plant — remained offline this morning. But Roark, the ERCOT spokeswoman, said that the grid operator was unable to say which plants remained offline today "because this is considered protected information under market rules in a competitive market."